Nickel plating brightener



United States Patent 3,190,821 NICKEL PLATING lBRIGHTENER Hans Giinther Todt, Berlin-Tempelhof, Germany,

, assignor to Schering, A.G., Berlin, Germany No Drawing. Filed Jan. 23, 1 962, Ser. No. 168,229 Claims priority, application Germany, Feb. 10, 1961, Sch 29,218 12 Claims. (Cl. 204-49) This invention relates to the electrodeposition of-n ickel, and more particularly to organic compounds which may be added to conventional nickel plating electrolytes, and whichcause the normally dull nickel deposit to be bright and lustrous.

It is known that small amounts of certain organic compounds when added to nickel plating electrolytes have a beneficial effect on the appearance of the nickel coatings produced. Best results are usually obtained with combinations of at least two brightening agents, a primary one of which maybe a heterocyclic organic nitrogen compound, whereas the other one is an aliphatic or aromatic sulfonic acid, sulfonarnide, or sulfonimide.

It is characten'stic of many known combinations of the aforementioned type that increasing amounts of primary agents when added to the electrolyte cause the nickel deposits to become brittle. The brightness and levelness of the nickel deposited also increases with the amount of primary brightener added, and his commonly found that the best possible levelling and brightening effect can be achieved only at a primary brightener concentration high enough to cause spontaneous formation of hairline cracks in the deposit, or mechanical failure of the deposit when the base material is deformed in flexure after ele-ctro-deposition.

Heterocyclic organic nitrogen compounds have previously been found to be particularly effective primary brigh-teners when employed singly or in conjunction with such secondary brighteners as the aforementioned sulfonic acids, sulfonamides, and sulfonimides. known nitrogen bearing cyclic compounds as a class have anunfavorable efiect on the ductility of the nickel coating.

It has now been found that the desired levelling and brightening effect can be achieved in otherwise conventional nickel plating electrolytes without loss of ductility by adding to the electrolytes brighteners of the general are ring systems including at least one nitrogen atom in their ring structure, R is a negatively charged radical, R is an anion, and n is an integer between one and five.

The brighteners of the invention are salt-like compounds in which two nitrogen bearing ring systems are connected by the positive charge of one-ring system and the negative charge of a radical attached to the other ring system. Suitable ring systems arejderived from pyridine, the diazines, such as pyrimidine, and py-r-azi-ne, benzopyridines, such as quinoline and isoquinoline, and benzodiazines, such as quinazoline and quinoxaline. The cyclic cores of these ring systems may be substituted at one or more carbon atoms by lower alkyl and alkenyl radicals such as methyl, ethyl, or vinyl radicals, by lower alkoxy radicals such as methoxy and ethoxy radicals, by loweralkaminoradicals such as methylamino and ethylamino radicals, by lower alkanoyl groups such as wherein Yet, the p extent that hairline cracks spontaneously form. The

3,199,821 Patented June 22,- 1965 "ice the acetyl group, by oxy, cyano or amino radicals, and by halide and formyl radicals.

The preferred negatively charged radicals R are the the nickel sulfamate bath, or the nickel fluoborate bath.

TABLE I Pyridinium-(pyridinium-N-a-cetate) chloride Pyridinium-(pyridinium-N-acetate) iodide Pyridinium-(pyridinium-N-propionate) chloride Pyridinium-(pyridinium-N-butylsulfonate) chloride Pyridinium-(pyridinium-N-methylsulfonate) chloride 4-methylpyridinium-(pyridinium-N-acetate) chloride 4-cyanopyridinium (pyridinium-N-ethylsulfonate) chloride Pyn'dinium-(3-acetylpyridinium-N-acetate) chloride Pyridinium-(2-chloropyridiniurn-N-acetate) chloride Pyridinium-(2,6-dimethylpyridinium-N-acetate) bromide 3-vinylpyridinium-(3-vinylpyridinium-N-propionate) bro- -mide 3-aminopyridinium-(3-aminopyridinium-N-acetate) chlo ride I 4-ethoxypyridinium-(*4-ethoxypyridinium-N-methylsulfonate) chloride Pyridinium-(pyridinium-N-methylsulfonate) chloride Pyridazinium-(pyridinium-N-acetate) chloride Pyridazinium-(pyridazirlium-N-acetatc) chloride Quinolinium-(pyridinium-N-acetate) chloride Quinolinium-(quinolinium-N-acetate) chloride Quinolinium-(quinolinium-N-ethylsulfonate) bromide 4-carbinolquinolinium-(quinolinium-N-acetate) chloride 4-mcthoxyquinolinium-(quinolinium-N-acetate) chloride Isoquinolinium-(quinolinium N methylsulfonate) bromide Benzopyridinium-(benzopyridinium-N-acetate) chloride Pyridinium-(pyridinium-N-acetate) hydroxide The compounds may be readily prepared by reacting heterocyclic bases with halogencarboxylicor halogenalkyl-sulfonic acids in aqueous or preferable organic solvent solution and, if necessary, by heating to reaction temperature.

A more detailed practice is illustrated by the following example:

2 moles of pyridine and 1 mole of chloroacetic acid are dissolved in acetone and boiled for 5 hours. The pyridinium-(pyridinium-N-acetate) chloride which precipitates is filtered off and dried. All the compounds mentioned maybe prepared by substituting equirnolecular amounts of the corresponding starting materials in the.

and 0.8 gram per liter. It will be noted that this range ishigher by an order of magnitude than the range of permissible concentrations of known brighteners which are pyridine or quinoline derivatives. These know-n bright eners when present in the ele'ctrolyte at concentrations as about 0.08 gram per liter embrittle nickel deposits to the bright nickel deposits obtained at the much higher concentrations at which the brighteners of the invention are preferably employed are fully ductile and permit severe deformation of the base metal.

The brightening compounds of the invention have a strong inhibitor effect. As it is possible to employ them at relatively high concentrations without loss of desirable mechanical properties in the nickel deposit, electrolytes including the brighteners of the invention have excellent levelling propertes, and are superior in this respect to the best known brighteners based on pyridine or quinoline derivatives. Nickel plated objects having satisfactory surface fiatness and high luster may thus be obtained by nickel plating on coarsely prepared base metal.

The nitrogen bearing heterocyclic compounds of the invention are effective brighteners when employed singly. Greatest brightness and best levelling are achieved when the brighteners of the invention are employed jointly with known secondary brighteners such as aliphatic and aromatic sulfonic acids, sulfonamides, and sulfonimides. The nickel salts, alkali metal salts, and other soluble salts of the sulfonic acids which are compatible with the plating solution will be understood to be included in the term sulfonic acid as employed in this specification and the appended claims.

Representative examples of the well known class of secondary brighteners which cooperate with the brightening compounds of the invention in a basic manner are listed in Table II.

TABLE II Vinylsulfonic acid Allylsulfonic acid Propyne sulfonic acid Benzenemonosulfonic acid m-Benzenedisulfonic acid 1,3,5-benzenetrisulfonic acid mand p-Chl-orobenzenesulfonic acids o-, mand p-Brom'obenzenesulfonic acids o-, mand p-Formylbenzenesulfonic acids The several isomeric formylbenzenedisulfonic acids Naphthalenesulfonic acid, both a and ,8 Naphthalenedisulfonic acid Naphthalenetrisulfonic acid Diphenylsulfonic acid Allylsulfonamide Benzenesulfonamide m-Benzenedisulfonamide 1,3,S-benzenetrisulfonamide o-, mand p-Toluenesulfonamides o-, mand p-Formylbenzene sulfonamides o-, mand p-Chlorobenzenesulfonamides o-, mand p-Bromobenzenesulfonamides o-Benzoylsulfonimide N-acetyl benzene sulfonimide Dibenzene-disulfonimide Di-p-tolyl-disulfonimide As is well known, the concentration of the secondary brighteners of the type exemplified by the compounds listed in Table II is not critical. They are effective to some extent at a concentration as low as 0.1 gram per liter, and may be present in the electrolyte to the limit of their solubility. For practical purposes, a concentration range of 0.3 gram per liter to 3.0 grams per liter is preferred when the secondary brighteners are employed jointly with the heterocyclic brightening agents of the invention.

It will be understood that the addition agents usually employed in nickel plating electrolytes to control pore formation due to hydrogen bubbles, wetting agents and the like may be employed concurrently with the brighteners and brightener combinations of the invention. The novel brighteners are also compatible with cobalt salts and many known brighteners so that those skilled in the art will find it possible to modify existing bright nickel plating electrolytes by gradually replacing conventional brighteners with those of the invention.

Nickel plating electrolytes and preferred conditions of their operation are given in the following examples, but it will be understood that the invention is not limited to the specific brightening compounds mentioned in these examples, and that other brighteners satisfying the structural requirements initially set forth, and more specifically the compounds listed in Table I may be substituted for the primary brighteners mentioned in the examples without materially affecting the results achieved.

Example I Nickel sulfate grams per liter 260 Nickel chloride d0 50 Boric acid d0 40 Sodium o formylbenzenesulfonate do 2.0 Pyridinium-(pyridinium-N-acetate) chloride do 0.6 Temperature, C. 55 pH 4.6 Cathode current density, actual, amperes per square decimeter 0.5 to 6.0 Cathode current density, average, amperes per square decimeter 5.0

Example II Nickel sulfate "grams per liter..- 240 Sodium chloride do 40 Boric acid do 30 Sodium vinylsulfonate do 0.5 O-Benzoylsulfonimide do 0.5 Pyrimidinium-(pyridinium-N-methylsulfonate) chloride grams per liter-.. 0.4 Temperature, C. '50

Cathode current density, actual, amperes per square decimeter 0.5 to 5.0 Cathode current density, average, amperes per square decimeter 4.0

Example III Nickel fiuoborate grams per Men. 340 Nickel chloride do 20 Sodium 1-f0rmyl-2,4-benzenedisulfonate do 2.0 p-Toluenesulfonamide do 0.4 Quinolinium-(quinolinium-N-acetate) chloride grams per liter 0.4 Temperature, C. 55 pH 3.8 Cathode current density, actual, amperes per square decimeter 0.6 to 15 Cathode current density, average, amperes per square decimeter 12.0

Example IV Nickel sulf-amate grams per liter 300 Nickel chloride do.. 30 Boric acid do 30 Sodium vinylsul-fonate d-o 0.5 Dibenzene-disulfonimide do.... 0.5 4 Cyanopyridinium (pyridinium N propylsulfo nate)chloride grarns per liter 0.4 Temperature, C. 40 pH 4.0 Cathode current density, actual, amperes per square decimeter 0.5 to 6.0 Cathode current density, average, amperes per square decimeter 5.0

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims.

I claim:

1. An electrolyte for the electrodeposition of bright ductile nickel coatings comprising in aqueous solution at least one nickel salt and a brightener which is an organic heterocyclic nitrogen compound of the formula are nitrogen bearing rings, 11 is an integer between 1 and 5, and R is an anion selected from the group consisting of halogen and the hydroxyl radical.

2. An electrolyte for the electrodeposition of bright ductile nickel coatings comprising in aqueous solution at least one nickel salt and a brightener which is an organic heterocyclic nitrogen compound of the formula are nitrogen bearing rings, n is an integer between 1 and 5, and R is an anion selected from the group consisting of halogen and the hydroxyl radical.

6. An electrolyte for the electrodeposition of bright ductile nickel coatings comprising in aqueous solution at least one nickel salt and a brightener which is an organic heterocyclic nitrogen compound of the formula wherein n is an integer between 1 and 5,

wherein wherein 6 Y -R' is an anion selected from the group consisting of a halogen and a hydroxyl radical.

4. An electrolyte as set .forth in claim 3, wherein said brightener is present in said electrolyte in a concentration between substantially 0.1 gram per liter and 3 grams per liter.

5. An electrolyte as set forth in claim 3, wherein said brightener is present in said electrolyte in a concentration between substantially 0.1 to 0.8 gram per liter.

6. An electrolyte as set forth in claim 3, further comprising as a secondary brightener a compound selected from the group consisting of aliphatic and aromatic sulfonic acids.

7. An electrolyte as set forth in claim 6, wherein the concentration of said secondary brightener is at least 0.1 gram per liter and not greater than the solubility of said secondary brightener in said electrolyte.

8. An electrolyte as set forth in claim 6, wherein the concentration of said secondary brightener is between 0.3 and 3.0 grams per liter.

9. An electrolyte as set forth in claim 3, wherein said brightener is a halide of pyridinium-(pyridinium-N-acetate).

10. An electrolyte as set forth in claim 3, wherein said brightener is a halide of pyridinium (pyridinium-N-methylsulfon-ate) '11. An electrolyte as set forth in claim 3, wherein said brightener is a halide of quinolinium-(quinolinium N- acetate.)

12. An electrolyte as set forth in claim '3, wherein G and are pyridin-ium rings, R is chlorine, and n is 1.

References Cited by the Examiner UNITED STATES PATENTS 2,644,789 7/53 Shenk 204-49 2,839,460 6/58 Foulke et al. 204-49 3,008,883 11/61 Passal 204-49 FOREIGN PATENTS 1,004,011 3/57 Germany. 1,092,744 11/ 6.0 Germany.

638,868 6/50 Great Britain.

LTOHN H. MACK, Primary Examiner. MURRAY TILLMAN, Examiner. 

3. AN ELECTROLYTE FOR THE ELECTRODEPOSITION OF BRIGHT DUCTILE NICKEL COATINGS COMPRISING IN AQUEOUS SOLUTION AT LEAST ONE NICKEL SALT AND A BRIGHTENER WHICH IS AN ORGANIC HETEROCYCLIC NITROGEN COMPOUND OF THE FORMULA 